Negative PDO may turn U.S. Midwest drier later this year
Ocean surface water temperatures off the North America Pacific Coast have shown a steady cooling trend in recent weeks. This trend has occurred while the north-central Pacific Ocean experiences warming ocean water. This phenomenon is associated with a negative phase of Pacific Decadal Oscillation (PDO). World Weather Inc. says the ocean surface temperature changes recently have been reinforcing the negative PDO event at a time when normally negative PDO weakens. This year’s negative PDO has been strengthening in recent weeks and it has been significantly negative for 21 straight months. There has been no other time since 1950 that PDO was strongly negative for such a long period of time.
At the same time, NOAA’s ENSO forecast model continues to predict a strong evolution toward El Niño late this spring and early summer. World Weather says 1957 and 1976 are the two years most like this one in which a multi-year La Niña was followed by El Niño, with 1976 being the best comparable year.
World Weather concludes, “The sudden change from a persistent multi-year La Niña event to an aggressive El Niño would leave the atmosphere confused because of significantly different weather pattern influences around the world. There would be a period of months in which areas of dryness and wet biased conditions may evolve in various places in the world as the atmosphere quickly shifts from the La Niña pattern to El Niño. During that period of confusion, if the PDO is still strongly negative it will help induce stronger ridge building in a part of North America and if that happens forecasters, traders and producers may be surprised to see dryness returning to a part of the region from the central Plains into a part of the Midwest. That does not mean a full-blown drought, but reduced precipitation and warmer temperatures for some areas might induce some crop stress.”
Perspective: The 1976 growing season was not favorable for corn and soybean yields. The 1976 corn yield of 88.0 bu. per acre was 90.7% of previous record. The soybean yield of 26.1 bu. per acre was 90.3% of the previous record.
